The use of PTC thermistors for realizing anti-condensate resistances is known.
PTC thermistors are devices made of conductive or semiconductive materials that have a varying resistance depending on temperature; consequently, PTC thermistors have the advantageous chance of self-regulating themselves depending on temperatures and in this way they are not subjected to overheating, even in case an adequate heat removal is prevented (for example, profile clogging, accidental heat sink coverage with any object, etc.). In particular, anti-condensate resistances using PTC thermistors are, in the majority of cases, composed of a heat sink made in a single aluminum profile inside which the PTC thermistor is arranged and segregated through closing plugs; however, the technical disadvantages of such arrangement are numerous. First of all, the realization of the heat sink in a single extrusion prevents the black anodization of its internal surfaces and therefore heat is for a good part transmitted through conduction instead of radiance; under these conditions, therefore the heat sink must be unavoidably manufactured with a certain minimum thickness in order to guarantee a good conduction level.
Moreover, crimping of the heat sink generally occurs through profile bending, this imposing a minimum height of the heat sink that is much greater than the height of the PTC thermistor, with consequent negative effects in terms of encumbrance and manufacturing costs.
It is also known that in existing embodiments, PTC thermistors are kept in position inside the heat sink through more or less complex mechanical arrangements, such as screws, bolts or springs, this obviously increasing their complexity and manufacturing costs. Such internal locking systems must further allow the thermal expansion of the heating element keeping an adequate contact load, which is as much as possible constant.
Such known anti-condensate resistances with PTC thermistors moreover exist also in a forced-ventilation version through an external fan; such fan however, in order to be able to be simply supplied directly through an electric network connection, is generally at 230V, thereby resulting relatively costly, encumbrant and oversized with respect to the power level to be dissipated.
Moreover, typically known and used closing plugs of a heat sink guarantee generally mediocre tightness levels.
The currently-used securing systems for anti-condensate resistances with PTC thermistors are normally made of metallic material, typically aluminum, to be able to resist thermal stresses; moreover, they are composed of many pieces: typically a carrier structure and various mobile and/or elastic parts (for example springs) that allow its elastic mechanical locking.